1. Field of the Invention
The present invention relates to a drive control device of an intake valve open/close motor for controlling an air-intake of an engine. More specifically, the invention relates to improvement of an engine air-intake control device arranged such that a monitoring control circuit is added to a drive control circuit of the above-mentioned motor and a power feed with respect to the above-mentioned motor is interrupted at the time of occurrence of any abnormality.
2. Description of the Related Art
An air-intake control device that controls by means of an electromotive motor an air-intake throttle-valve opening of an engine in accordance with a depression degree of an accelerator pedal has been popularly employed in practical use. To improve safety in this type of electronic throttle control, however, a monitoring control circuit is usually added with respect to a drive control circuit of an electromotive motor, and the following control is implemented. In this control, a power feed to an electromotive motor is interrupted by means of a driving switch element and a power supply relay at the time of occurrence of any abnormality, and a throttle valve opening is mechanically returned to be in an initial state by means of a return spring.
According to the Japanese Patent Publication (unexamined) No. 097087/2000, “a throttle valve control device” is disclosed. In this throttle valve control device, throttle valve control means acting as a drive control circuit, main engine control means acting as a monitoring control circuit, and a motor power supply relay are used; the throttle valve control means and main engine control means include a mutual monitoring function and a self-diagnosis function; and the above-mentioned motor power supply relay is interrupted, and then a throttle valve opening is made to return to an initial position when a serious error is detected.
Besides, according to the Japanese Patent Publication (unexamined) No. 235598/2002, “a vehicle control device” is disclosed. In this vehicle control device, e.g., in the case where a microprocessor contained in an on-vehicle electronic device such as electronic throttle control device runs away, this trouble is detected by means of a watchdog timer to start up the microprocessor again; further, the fact that an error operation has occurred is stored in a storage element to interrupt a load relay for switching a load power supply such as throttle valve open/close motor.
This prior art was made intending to improve safety by an arrangement such that a motor power feed circuit continues to be in an interruption state until a power supply switch has once been interrupted although the microprocessor is immediately started up again in case of a temporary noise malfunction.
In the prior arts as described above, the drive control circuit controls an ON/OFF ratio of the driving switch element to control the amount of power feed with respect to the motor for controlling an intake valve opening of an engine, and opens a circuit of the driving switch element at the time of occurrence of any abnormality; as well as a power supply relay for the motor is also interrupted by the monitoring control circuit, so that a dual system is built up in both aspects of a control system and switching circuit system.
However, on the supposition that an improper soldering at an electronic substrate, getting mixed of a conductive foreign substance, breakdown of an electronic part or the like occur, any error takes place in a connection relation between the drive control circuit and the driving switch element and a connection relation between the monitoring control circuit and a power supply relay electromagnetic coil. Consequently, a problem exits in that a dangerous state occurs in which the drive/stop of the driving switch element or power supply relay is not always performed reliably.